Increased coated-platelet levels in chronic haemodialysis patients

Increased procoagulant platelet levels are predictive of death in COVID-19

Prior research has identified abnormal platelet procoagulant responses in COVID-19. Coated-platelets, a form of procoagulant platelets, support thrombin formation and are elevated in ischemic stroke patients with increased risk for recurrent infarction. Our goal was to examine changes in coated-platelet levels over the course of COVID-19 infection and determine their association with disease severity, thrombosis, and death. Coated-platelet levels were assayed after admission and repeated weekly in COVID-19 patients, and in COVID-19 negative controls. Receiver operator characteristic (ROC) analysis was used to calculate area under the curve (AUC) values for a model including baseline coated-platelets to predict death. Kaplan–Meier and Cox proportional hazards analysis was used to predict risk for death at 90 days. We enrolled 33 patients (22 with moderate and 11 with severe infection) and 20 controls. Baseline coated-platelet levels were lower among moderate (mean ± SD; 21.3 ± 9.8%) and severe COVID-19 patients (28.5 ± 11.9%) compared to controls (38.1 ± 10.4%, p < 0.0001). Coated-platelet levels increased during follow-up in COVID-19 patients by 7% (relative) per day from symptom onset (95% CI 2–12%, p = 0.007). A cut-off of 33.9% for coated-platelet levels yielded 80% sensitivity and 96% specificity for death at 90 days, with resulting AUC of 0.880 (95% CI 0.680–1.0, p = 0.0002). The adjusted hazard ratio for death in patients with coated-platelet levels > 33.9% was 40.99 when compared to those with levels ≤ 33.9% (p < 0.0001). Platelet procoagulant potential is transiently decreased in most patients during COVID-19; however, increased baseline platelet procoagulant levels predict death. Defining the mechanisms involved and potential links with aging may yield novel treatment targets.

Thrombocytopathies: Not Just Aggregation Defects-The Clinical Relevance of Procoagulant Platelets

Platelets are active key players in haemostasis. Qualitative platelet dysfunctions result in thrombocytopathies variously characterized by defects of their adhesive and procoagulant activation endpoints. In this review, we summarize the traditional platelet defects in adhesion, secretion, and aggregation. In addition, we review the current knowledge about procoagulant platelets, focusing on their role in bleeding or thrombotic pathologies and their pharmaceutical modulation. Procoagulant activity is an important feature of platelet activation, which should be specifically evaluated during the investigation of a suspected thrombocytopathy.

Increased platelet procoagulant potential predicts recurrent stroke and TIA after lacunar infarction

BACKGROUND

Mean levels of coated-platelets, a subset of highly procoagulant platelets, are decreased in patients with lacunar as compared to those with non-lacunar stroke. Elevated coated-platelets are associated with increased risk for recurrent infarction in non-lacunar stroke and predict incident stroke after transient ischemic attack (TIA).

OBJECTIVE

We investigated if coated-platelet levels are predictive of recurrent cerebral ischemia following lacunar stroke.

METHODS

Coated-platelet levels were assayed in consecutive patients with acute lacunar stroke, who were followed for up to 12 months. Cox proportional hazards regression analysis was used to estimate the combined risk of stroke and TIA at 12 months according to initial coated-platelet levels.

RESULTS

We enrolled a total of 109 lacunar stroke patients. Eight events were recorded over a mean follow-up period of 10.8 months. A cut-off of 42.6% for coated-platelet levels yielded a sensitivity of 0.75 (0.35-0.97; 95% confidence interval [CI]), specificity of 0.92 (0.85-0.97), positive predictive value of 0.43 (0.26-0.62), and a negative predictive value of 0.98 (0.93-0.99) for recurrent stroke/TIA. The adjusted hazard ratio for recurrent stroke/TIA in patients with coated-platelet levels ≥ 42.6% was 23.9 (95% CI: 4.26-134.4) when compared to those with levels < 42.6%.

CONCLUSIONS

Identification of increased platelet procoagulant potential may improve our ability to identify patients at higher risk of recurrent stroke/TIA following a lacunar stroke. Further study of mechanisms involved is warranted and may yield novel targets for prevention and treatment.

Clopidogrel use and smoking cessation result in lower coated-platelet levels after stroke

Coated-platelets are a subset of highly procoagulant platelets elevated in patients with non-lacunar ischemic stroke and associated with stroke recurrence. Cross-sectional studies in controls have shown that smoking is associated with higher coated-platelet levels while chronic use of serotonin reuptake inhibitors (SSRIs), statins or aspirin is associated with lower coated-platelet levels. We now investigate if initiation of treatment with SSRIs, statins, clopidogrel, aspirin or oral anticoagulants and smoking cessation impacts coated-platelet levels at 90 days after ischemic stroke. Coated-platelet levels, reported as percent of cells converted to coated-platelets, were measured in 87 consecutive patients with stroke at baseline and repeated at 90 days. Repeated-measure ANOVA was used to determine if initiation of treatment with individual medications or smoking cessation impacted coated-platelet levels. Decreased coated-platelets levels at 90 days as compared to baseline were observed after initiation of treatment with clopidogrel (p = .0001, partial η² = 0.17) and smoking cessation (p = .014, partial η² = 0.10). Initiation of treatment with SSRIs, statins, aspirin or oral anticoagulants did not result in significant changes in coated-platelet potential. These novel longitudinal data suggest that clopidogrel therapy and smoking cessation attenuate coated-platelet potential at 90 days after ischemic stroke.

Acute hemorrhagic complications are associated with lower coated-platelet levels in non-lacunar brain infarction

BACKGROUND

Coated platelets are procoagulant platelets observed upon dual agonist stimulation with collagen and thrombin. Coated-platelet levels are elevated in patients with non-lacunar ischemic stroke and decreased in patients with spontaneous intracerebral hemorrhage as compared with controls.

OBJECTIVE

To investigate whether acute hemorrhagic complications occurring during the initial hospital admission for non-lacunar ischemic stroke are associated with lower coated-platelet levels.

PATIENTS/METHODS

Coated-platelet levels were determined in 385 consecutive patients with non-lacunar stroke. Hemorrhagic complications were defined as either intracranial hemorrhage or significant extracranial bleeding (drop in hemoglobin of ≥ 2 g dL(-1) ). The rate of acute hemorrhagic complication was compared among subjects categorized into tertiles of coated-platelet levels using an exact Cochrane-Armitage trend test. Logistic regression was used to estimate the adjusted odds of hemorrhagic complication associated with coated-platelet levels.

RESULTS

Hemorrhagic complications were present in 15 (3.9%) cases. Of these, four had intracranial hemorrhage and 11 had extracranial hemorrhage. The occurrence of hemorrhagic complications differed among the coated-platelet tertiles: 10.2% for the first tertile (coated-platelet levels < 35.5%), 1.5% for the second tertile and 0% for the third tertile (coated-platelet levels ≥ 47.5%, trend test). Logistic regression showed that the odds of hemorrhagic complication in those with levels < 35.5% were 14.59 times the odds for patients with levels ≥ 35.5% (95% CI: 3.24-65.7).

CONCLUSIONS

Lower levels of procoagulant platelets are associated with acute hemorrhagic complications following non-lacunar ischemic stroke. These results suggest a role for coated-platelets in risk/benefit assessment in the early stages of stroke.

Coated-Platelet Levels Increase with Number of Injuries in Patients with Mild Traumatic Brain Injury

Coated-platelets are procoagulant platelets that are elevated in stroke and are associated with stroke recurrence. In a previous study, prompted by data showing an increased risk for stroke following traumatic brain injury (TBI), we found that coated-platelet levels are elevated in patients with combat-related mild TBI (mTBI) several years after the injury, compared with controls. We now investigate in an expanded patient population whether parameters commonly recorded in mTBI are related to increased coated-platelet potential. Coated-platelet levels were assayed in 120 mTBI patients at intervals ranging from 6 months to 10 years from the last injury. Correlations were calculated between coated-platelet levels and age, gender, race/ethnicity, loss of consciousness, alteration in consciousness, post-traumatic amnesia, number of injuries, mechanism of injury, time since first and last injury, smoking, medications that may influence coated-platelet levels, and pertinent comorbid conditions. Significant correlations were detected between coated-platelet levels and number of injuries (p = 0.026), gender (p = 0.01), and time since last injury (p = 0.04). A multi-variable linear model analysis, including these three parameters and an additional three parameters (race/ethnicity, smoking, and mechanism of injury) that reached a p value of <0.2, showed that the number of injuries were predictive of coated-platelet levels (p = 0.004). These results support a mechanistic link between increased coated-platelet levels and repeated injuries in mTBI. Long-term studies will be required to determine the impact of increased prothrombotic potential in mTBI patients.

Lower Coated-Platelet Levels Are Associated With Increased Mortality After Spontaneous Intracerebral Hemorrhage

BACKGROUND AND PURPOSE

Coated-platelets are highly procoagulant platelets observed on dual-agonist stimulation with collagen and thrombin. Coated-platelet levels are decreased in patients with spontaneous intracerebral hemorrhage when compared with controls and inversely correlated with bleed volume. We sought to investigate whether coated-platelets are associated with increased mortality at 30 days after spontaneous intracerebral hemorrhage.

METHODS

Coated-platelet levels were assayed in 95 consecutive patients with spontaneous intracerebral hemorrhage. The main outcome was mortality at 30 days according to coated-platelet levels at enrollment. Subjects were grouped into tertiles of the observed coated-platelet level distribution. Groups defined by tertile of coated-platelet level were compared using either ANOVA or a Kruskal-Wallis test for small group size for continuous measures and an exact Cochrane-Armitage trend test for categorical measures. Logistic regression was used to estimate the adjusted odds of death within 30 days associated with coated-platelet levels.

RESULTS

Cumulative mortality at 30 days was 23% (22 subjects). Mortality at 30 days differed among the coated-platelet tertiles: 44% for the first tertile (lowest coated-platelet levels), 19% for the second tertile, and 6% for the third tertile (trend test; P=0.0004). Logistic regression examining the association between mortality and coated-platelet levels showed that the odds of death at 30 days in those with levels <27% (n=47) were 6.83× the odds for patients with levels ≥27% (95% confidence interval, 2.10-22.23).

CONCLUSIONS

These results support a link between impaired coated-platelet potential and outcome in intracerebral hemorrhage.

Coated-platelets improve prediction of stroke and transient ischemic attack in asymptomatic internal carotid artery stenosis

BACKGROUND AND PURPOSE

Coated-platelets, a subset of procoagulant platelets observed on dual agonist stimulation with collagen and thrombin, support a robust prothrombinase activity and provide a unique measure of platelet thrombotic potential. Coated-platelet levels are increased in large artery stroke, and higher levels are associated with early stroke recurrence, suggesting a potential role for risk stratification in asymptomatic patients with carotid artery stenosis.

METHODS

Three-hundred twenty-nine consecutive patients with technically adequate carotid Doppler evaluation without stroke or transient ischemic attack (TIA) in the previous 6 months were enrolled as part of a prospective cohort study conducted during a 40-month period. The main outcome was occurrence of stroke or TIA according to coated-platelet levels and internal carotid stenosis severity at enrollment. The optimal cutoff value of coated-platelet levels was determined by recursive partitioning analysis. Event-free survival was estimated using Kaplan-Meier and Cox proportional hazards regression analyses.

RESULTS

A cutoff of ≥45% for coated-platelet levels in combination with stenosis≥50% yielded a sensitivity of 0.78 (95% confidence interval, 0.51-1.0), specificity of 0.92 (0.89-0.95), positive predictive value of 0.21 (0.07-0.34), and a negative predictive value of 0.99 (0.98-1.0) for ipsilateral stroke or TIA. The incidence rate of ipsilateral stroke or TIA for patients with ≥50% stenosis and ≥45% coated-platelets was 21.5 per 100 person-years versus 1.27 per 100 person-years for patients with ≥50% stenosis and <45% coated-platelets (P<0.0001).

CONCLUSIONS

Coated-platelet levels identify asymptomatic carotid stenosis patients at high risk for stroke or TIA, which suggests a role for coated-platelets in risk stratification before revascularization.

Cerebral microbleeds in nonlacunar brain infarction are associated with lower coated-platelet levels

BACKGROUND

Coated-platelets are a subset of platelets with high procoagulant potential observed on dual-agonist stimulation with collagen and thrombin. Coated-platelet levels are elevated in patients with nonlacunar ischemic stroke compared with controls, although the presence of early hemorrhagic transformation is associated with lower coated-platelet levels. In contrast to infarction, patients with spontaneous intracerebral hemorrhage have lower coated-platelet levels, and these levels inversely correlate with bleed size. Cerebral microbleeds (CMBs) represent previous small hemorrhagic occurrences. We undertook a pilot study to investigate coated-platelet production and the presence of CMBs in patients with nonlacunar ischemic stroke.

METHODS

Coated-platelet levels were determined in 110 consecutive patients with a diagnosis of nonlacunar stroke. Microbleeds were identified using the published criteria by an experienced stroke neurologist. Coated-platelet levels were compared statistically between patients with and without CMBs using the nonparametric Wilcoxon rank sum test.

RESULTS

Coated-platelet levels (median [interquartile range]) for all patients were 44.1% [34%-51.2%]. CMBs were detected in 22 patients (20%); these patients had significantly lower coated-platelet levels compared with those without CMBs (35.6% [22.6%-47.2%] versus 45.1% [36.1%-51.5%]; P = .025), whereas other demographic and clinical factors did not differ significantly.

CONCLUSIONS

The presence of CMBs in patients with nonlacunar ischemic stroke is associated with lower levels of coated-platelets. Larger prospective studies are needed to better establish the potential connection between altered coated-platelet synthesis, microbleeds, cerebral infarction, and possible hemorrhage-prone vascular changes.

Higher levels of coated-platelets are observed in patients with subarachnoid hemorrhage but lower levels are associated with increased mortality at 30 days

BACKGROUND

Coated-platelets are procoagulant platelets observed upon dual agonist stimulation with collagen and thrombin. Coated-platelet levels are elevated in non-lacunar ischemic stroke compared to either lacunar stroke or controls. In contrast, coated-platelet levels are decreased in spontaneous intracerebral hemorrhage (ICH) and inversely correlated with bleed size. We now report the first investigation of coated-platelets in patients with subarachnoid hemorrhage (SAH).

METHODS

Coated-platelet levels were determined in 40 consecutive patients with spontaneous SAH and in 40 controls. Results are reported as percent of cells converted to coated-platelets. Mortality at one month was recorded for all patients.

RESULTS

Coated-platelet levels (mean ± SD) were significantly higher in SAH patients compared to controls (41.8 ± 11.4% vs. 30.7 ± 12.2%, p<0.0001). Among all patients, mortality at 1 month was 20% (8 deaths). Patients were analyzed according to tertiles of coated-platelet levels (split at <36.7%, 36.7-46.2%, >46.2%). The 1-month mortality differed significantly between the coated-platelet tertiles (p=0.01) with 46% mortality (6/13) among patients in the lowest tertile (lowest levels) compared to 14.3% (2/14) among those in the middle tertile and 0% in the highest tertile.

CONCLUSIONS

Coated-platelet levels are higher in SAH patients compared to controls. However, lower coated-platelet levels are associated with increased 1-month mortality in SAH patients, a finding compatible with prior observations of an inverse relationship between coated-platelet levels and bleed volume in ICH. The current data support the role played by these prothrombotic platelets in thrombosis or hemorrhage and suggest a potential place for coated-platelet levels in predicting prognosis after SAH.

Elevated coated-platelets in symptomatic large-artery stenosis patients are associated with early stroke recurrence

Coated-platelets are a subset of platelets with increased procoagulant potential observed upon dual agonist stimulation with collagen and thrombin. These prothrombotic platelets are elevated in patients with non-lacunar ischemic stroke and decreased in patients with spontaneous intracerebral hemorrhage compared to controls. We now investigated coated-platelet synthesis in patients with symptomatic large-artery stenosis and explored the association between coated-platelet levels and stroke recurrence at 3 months in this population. Coated-platelet levels were determined in 60 patients with either acute stroke or transient ischemic attack due to large-artery stenosis and 60 controls. Recurrent stroke incidence at 3 months was stratified by tertiles of coated-platelet levels and compared among groups using a log-rank test. Large-artery stenosis patients had significantly higher coated-platelet levels than controls (mean ± SD, 42.0 ± 15.5% vs. 29.4 ± 13.5%, p < 0.0001). The 3-month cumulative incidence of recurrent stroke was 41% for the highest, 6% for the middle, and 5% for the lowest tertile of coated-platelet levels (p = 0.0045). These results show that elevated coated-platelet levels in patients with symptomatic large-artery stenosis are associated with early stroke recurrence.

Higher coated-platelet levels are associated with stroke recurrence following nonlacunar brain infarction

Coated-platelets are procoagulant platelets observed upon dual-agonist stimulation with collagen and thrombin. Coated-platelet levels are elevated in patients with nonlacunar (large-vessel) ischemic stroke and decreased in patients with spontaneous intracerebral hemorrhage as compared with controls. The purpose of this study was to investigate a possible relationship between coated-platelet levels and stroke recurrence in patients with nonlacunar ischemic stroke. We assayed coated-platelet levels in 190 consecutive patients with nonlacunar stroke who were followed for up to 12 months; 20 subjects experienced recurrent stroke. Subjects were categorized into tertiles of coated-platelet levels. The distributions of time-to-recurrent stroke were estimated for each tertile using cumulative incidence curves and compared statistically using a log-rank test. The cumulative incidence of recurrent stroke at 12 months differed among the coated-platelet tertiles: 2% for the first tertile (lowest coated-platelet levels), 18% for the second tertile, and 17% for the third tertile (overall log-rank test, P=0.019). These data suggest that higher levels of coated-platelets, measured shortly after a nonlacunar stroke, are associated with an increased incidence of stroke recurrence. This observation offers an additional tool for identifying patients at highest risk for stroke recurrence following a nonlacunar (large-vessel) infarct.

Platelet activation, coagulation activation and C-reactive protein in simultaneous samples from the vascular access and peripheral veins of haemodialysis patients

INTRODUCTION

Most studies of haemodialysis (HD) patients compare venous blood samples from controls with samples from the vascular access (VA) of HD patients. We hypothesised that VA samples may be more prothrombotic compared with venous samples.

METHODS

Samples were taken simultaneously from the VA and the contralateral antecubital vein, from 26 patients immediately before HD. Platelet function was assessed by (1) flow cytometric measurement of P-selectin expression and fibrinogen binding (±ADP) and 2) Ultegra rapid platelet function assay. Plasma soluble P-selectin, von Willebrand factor antigen, high sensitivity C-reactive Protein (hs-CRP), thrombin-antithrombin III complex and D-dimer measured by ELISA.

RESULTS

Thrombin receptor activating peptide-induced platelet aggregation (P < 0.001) and hs-CRP (P < 0.001) were higher in VA compared with venous samples. Unstimulated platelet fibrinogen binding (P = 0.016) and ADP-stimulated P-selectin expression (P = 0.008) were lower in VA compared with venous samples. The significant difference in hsCRP persisted when patients taking and not taking antiplatelet therapy were analysed separately, but platelet activation remained significantly different only in the nonantiplatelet group.

CONCLUSION

There are statistically significant differences between sampling sites, although samples from the VA do not appear to be more pro-thrombotic. Future studies comparing HD patients with controls should ensure uniformity of sampling sites to prevent inaccurate conclusions being drawn.

Coated-platelet levels are elevated in patients with transient ischemic attack

Transient ischemic attack (TIA) presents a medical management dilemma because of the high frequency of subsequent ischemic strokes. The ABCD2 score is designed to stratify the short-term risk for stroke in TIA patients. Coated-platelets, which are a subset of procoagulant platelets observed after dual agonist stimulation with collagen and thrombin, are increased in cortical ischemic stroke and decreased in spontaneous intracerebral hemorrhage. Because TIA increases the risk of subsequent ischemic stroke, we conducted a pilot study to investigate whether coated-platelet production is increased in patients with TIA (n = 60) compared with controls (n = 60). Coated-platelet levels were higher in TIA patients versus controls [mean ± standard deviation (SD), 38.4 ± 15.1% vs 31.0 ± 13.2%, P = 0.005], and a significant linear correlation was detected between ABCD2 scores and coated-platelet levels in TIA patients (P = 0.0003, r = 0.45). These findings lend support to the hypothesis that TIA and ischemic stroke represent a spectrum of conditions dependent on similar prothrombotic processes.

Coated-platelet levels and progression from mild cognitive impairment to Alzheimer disease

OBJECTIVES

Coated-platelets are a subset of platelets produced by dual-agonist activation with collagen and thrombin. These platelets retain full-length amyloid precursor protein on their surface, are elevated in patients with amnestic as compared to nonamnestic mild cognitive impairment (MCI), and correlate with disease progression in Alzheimer disease (AD). Prompted by these findings, we investigated the association between coated-platelet production in amnestic MCI and rate of progression to AD.

METHODS

Coated-platelet levels were assayed in 74 patients with amnestic MCI who were subsequently followed longitudinally for up to 36 months in an outpatient dementia clinic. Levels are reported as percent of cells converted into coated-platelets. Subjects were categorized into tertiles of coated-platelet levels. The distributions of time to progression to AD were estimated for each tertile using cumulative incidence curves and compared statistically using a log-rank test. Cox proportional hazards regression was used to adjust for potential confounders.

RESULTS

The 24-month cumulative incidence of progression to AD was different among tertiles: 4% for the first tertile (lowest coated-platelet levels), 13% for the second tertile, and 37% for the third tertile (overall log-rank test, p = 0.02). The hazard rate of progression to AD for patients in the highest coated-platelet tertile was 5.1 times that for patients in the lowest tertile (p = 0.04), whereas the hazard rate for the middle tertile was similar to that for the lowest tertile (hazard rate ratio = 1.5, p = 0.7).

CONCLUSIONS

Elevated coated-platelet levels in patients with amnestic MCI are associated with increased risk for progression to AD.

Lower coated-platelet levels are associated with early hemorrhagic transformation in patients with non-lacunar brain infarction

BACKGROUND

Coated-platelets, representing a subset of platelets with procoagulant potential, are elevated in patients with non-lacunar ischemic stroke and decreased in patients with spontaneous intracerebral hemorrhage. However, within the non-lacunar patient population there are individuals with lower levels of coated-platelets, which raises the possibility that these individuals would be susceptible to early hemorrhagic transformation (HT) of ischemic stroke.

OBJECTIVE

Because extremes in coated-platelet potential may be associated with either thrombotic or hemorrhagic events, we undertook a pilot study to investigate whether there is an association between coated-platelet production and the presence of early HT in patients with non-lacunar ischemic stroke.

PATIENTS AND METHODS

Coated-platelet levels were determined in 115 consecutive eligible patients with a diagnosis of non-lacunar ischemic stroke. Early HT was determined on CT scan examination and confirmed by MRI studies. The distribution of coated-platelet levels was summarized using the median and interquartile range (25th-75th percentiles) and compared statistically between patients with and without early HT using the non-parametric Wilcoxon rank sum test.

RESULTS

The median coated-platelet level in all non-lacunar stroke patients was 38.0% (interquartile range 30.5-48.3%). Early HT was detected in 11 patients (9.6%), and these patients had significantly lower coated-platelet levels compared with those without early HT [median 25.1% (interquartile range 20.4-35.5%) vs. 39.2% (31.6-49.5%), P = 0.003].

CONCLUSIONS

Lower levels of coated-platelets are associated with the presence of early HT in patients with non-lacunar ischemic stroke.